JPH08292744A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display device in which cross talk is greatly reduced. CONSTITUTION: The points, at which signal electrodes X1 to X8 and scanning electrodes Y1 to Y8 cross each other, correspond to the picture elements of a liquid crystal panel 1. Here, a signal side driving circuit 2 detects whether the display data of a certain scanning electrode have changed against the data of one previous scanning electrode or not. If there is no change, a normal signal voltage level is outputted. If there is a change, compensation voltages V2' or V4', which compensate for the effective voltage drop caused by the reduction in the sharpness of the waveforms by the change, are outputted for a certain time duration of the scanning period. Thus, the effective value reduction caused by the reduction in the sharpness of the waveform generated in the electrode X1, for example, is compensated for.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using a simple matrix type liquid crystal panel driven by a voltage averaging method.

[0002]

2. Description of the Related Art In recent years, with the widespread use of devices such as personal computers and word processors, as a display device attached to the devices, a liquid crystal which is lightweight and thin and can be driven by a battery instead of a large CRT which consumes a large amount of power. Display devices are widely used.

As a driving method of this liquid crystal display device, a simple matrix driving method and an active matrix driving method are known. Compared to the latter active matrix driving method, the former simple matrix driving method
Since each pixel arranged in a matrix does not require a non-linear element, it has advantages of relatively easy manufacturing and low cost. On the other hand, as the display capacity increases,
Due to its characteristics, display unevenness depending on the display pattern, so-called crosstalk occurs, and this tends to deteriorate the display quality.

The above display unevenness will be described below by exemplifying a simple matrix type liquid crystal display device using a voltage averaging method.

First, the structure of a simple matrix type liquid crystal display device will be described. As shown in FIG. 9, the conventional liquid crystal display device includes a plurality of scan electrodes Y1 to Y8 and a plurality of signal electrodes X.
A liquid crystal panel 101 in which 1 to X8 are arranged to intersect with each other is provided. Further, a scanning side drive circuit 103 for applying a voltage to the scanning electrodes Y1 to Y8 in a line sequential manner, and a signal electrode X.
1 to X8, a signal side drive circuit 102 that applies a signal voltage based on display data, a power supply circuit 104 that generates a voltage necessary to drive the scan side drive circuit 103 and the signal side drive circuit 102, and the scan The control circuit 105 controls the side driving circuit 103 and the signal side driving circuit 102.

The scan electrodes Y1 to Y8 are sequentially scanned,
At the time of selection, the selection voltage V1 supplied from the power supply circuit 104
Alternatively, when V5 is not selected, the non-selection voltage V3 supplied from the power supply circuit 104 is applied. On the other hand, an ON voltage or an OFF voltage supplied from the power supply circuit 104 is applied to the signal electrodes X1 to X8 corresponding to display data. As a result, the liquid crystal display element is driven.

The power supply circuit 104 is a signal side drive circuit 102.
Drive voltages V2 and V4 supplied to the scanning side drive circuit 103 and drive voltages V1 and V3 supplied to the scan side drive circuit 103.
It is designed to generate V5.

Further, the control circuit 105 outputs the display data D, the data shift clock CK, the scanning clock LP and the alternating signal FR to the signal side driving circuit 102, while the scanning clock is outputted to the scanning side driving circuit 103. LP, a scan start signal FLM, and an AC signal FR are output.

In this example, for convenience of explanation, the number of each of the above-mentioned electrodes is eight, and these electrodes are 1/8.
The case where the driving is performed with the duty and the inversion signal period for the AC driving is 3 scanning lines is described.

Next, the operation of each drive circuit of the liquid crystal display device configured as described above will be described with reference to the timing chart shown in FIG. 10 shows a pixel A (intersection of the signal electrode X2 and the scanning electrode Y2) and a pixel B (signal electrode X3 and the scanning electrode Y) on the liquid crystal panel 101 shown in FIG.
2 shows an ideal voltage waveform applied to the intersection point 2). It should be noted that on the liquid crystal panel 101 of FIG. 9, the pixels indicated by ◯ are in the lit state, and the pixels indicated by  are in the non-illuminated state.
Further, in FIG. 10, (a) shows the scanning clock LP,
9B shows the AC signal FR, and FIGS. 9C and 9D are shown in FIG.
Of the ideal signal-side voltage waveform applied to the signal electrodes X2 and X3, (e) of the ideal scanning-side voltage waveform applied to the scanning electrode Y2, (f) and (g) of the pixel A, The ideal voltage waveform applied to B is shown.

As is apparent from the waveforms applied to the pixels of FIGS. 10 (f) and 10 (g), equal effective voltages are applied to the pixels A and B in the ideal state, and the transmittance of the liquid crystal panel is high. There should be no difference in. However, in an actual liquid crystal panel, as shown in FIG. 9, when black and white alternating stripe display is performed on a white background, another background portion (for example, pixel B) on the same signal electrode as the stripe portion ( For example, it is known that display unevenness (crosstalk) occurs in which the luminance is darker than that of the pixel A) (indicated by diagonal lines in FIG. 9).

Since this type of crosstalk remarkably deteriorates the display quality, it is an important problem to be solved in a simple matrix type liquid crystal display device.

Next, the cause of crosstalk will be described. 11A shows the scanning clock LP, and FIG. 11B shows the alternating signal FR. In addition, FIG.
9D shows an ideal signal-side voltage waveform applied to the signal electrodes X2 and X3 in FIG. 9, and comparing effective values,
No difference is observed between the signal electrodes X2 and X3. However, in an actual liquid crystal panel, a blunt waveform as shown in FIGS. 11E and 11F is applied due to the internal resistance of the signal side drive circuit 102 and the resistance component of the signal electrode inside the liquid crystal panel. . Note that the blunted waveform is simplified and shown as a straight line in the figure, but it actually changes in accordance with the charging / discharging waveform to the capacity.

Therefore, as is clear from FIGS. 11 (e) and 11 (f), regarding the waveform of the voltage applied to the signal electrode by the stripe display, the signal electrode X3 having a large number of changes in the state of the shape is the signal electrode X2. Compared with this, the number of blunted portions is large, and the effective value of the voltage applied to the signal electrode X3 is reduced accordingly. Therefore, the pixel (for example, pixel B) on the signal electrode X3 looks darker than the pixel (for example, pixel A) on the signal electrode X2, and is recognized as crosstalk.

Therefore, in order to eliminate this crosstalk,
A method has been proposed in which a period in which the signal-side applied voltage waveform is inverted is provided only in a certain period of one scan line driving period (for example, JP-A-5-333315 and JP-A-41-276794). In this proposed technique, a period in which the signal-side applied voltage level is inverted is provided in a predetermined period of one scan line driving period, so that the waveform on the signal-side applied voltage is blunted even when there is no waveform blunting due to display data. Is generated to make the waveform blunt of the applied voltage on the signal side uniform to some extent, and crosstalk in stripe display can be reduced.

[0016]

However, the above-mentioned proposed technique has the following problems. That is, the above-mentioned proposed method is a method of causing waveform blunting even in a background portion that originally has no waveform blunting, and reducing the effective value of that portion to make it uniform, so that the number of signal electrodes provided in the entire liquid crystal panel is reduced. The voltage waveform applied to the signal electrodes in the background display portion, which occupies most of them, changes simultaneously in all the scanning periods, and a large waveform distortion occurs on the scanning electrode side via the capacitance of the liquid crystal layer. Therefore, there is a problem that crosstalk of a different type from the crosstalk of stripe display, that is, the crosstalk in which a black line is vertically displayed on a white background and becomes brighter at the top and bottom, is increased. there were. In addition, as the size of the liquid crystal panel increases, there is a problem that the degree of crosstalk of the other type, which is the latter type, greatly differs depending on the vertical and horizontal directions of the liquid crystal panel. However, there is a problem that power consumption is always close to the maximum regardless of the display pattern.

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a liquid crystal display device capable of significantly reducing crosstalk.

[0018]

According to another aspect of the present invention, there is provided a liquid crystal display device comprising a liquid crystal panel in which a liquid crystal layer is provided between a plurality of signal electrodes and a plurality of scanning electrodes which are arranged to intersect each other. A liquid crystal display device comprising: a signal side driving means for applying a voltage corresponding to display data for displaying the liquid crystal panel to the signal electrodes; and a scanning side driving means for sequentially applying a scanning voltage to the scanning electrodes. And voltage generating means for supplying the signal-side driving means and the scanning-side driving means with a voltage necessary for driving the signal-side driving means and the scanning-side driving means. If there is no change, the normal signal voltage level is output, and if there is a change, a correction voltage is applied to correct the effective voltage drop due to the waveform blunting. , Within the applicable scanning period It has a structure in which a certain period output Te, the objects can be achieved.

The liquid crystal display device according to the invention of claim 2 is
The voltage generating means is configured to generate the correction voltage of at least one level in addition to the normal signal voltage level as the voltage level supplied to the signal side driving means, and the signal side driving means is The output stage is configured to be able to selectively output at least one level of the correction voltage supplied from the voltage generating means in addition to the normal signal voltage level. Detecting whether the display data changes or not, and outputting the normal signal voltage level when there is no change, and when there is a change, outputting the correction voltage for a certain period within the corresponding scanning period. Is characterized by.

A liquid crystal display device according to the invention of claim 3 is
The voltage generating means has a function of generating at least one level of the correction voltage in addition to the normal signal voltage level as a voltage level to be supplied to the signal side driving means, and a certain period within a corresponding scanning period, A voltage switching unit that outputs the correction voltage instead of the normal signal voltage level and supplies the corrected voltage to the signal side driving unit is provided, and the output side of the signal side driving unit selects the normal signal voltage level. It is configured so that the output can be made to have a high impedance, and whether or not the display data of the scanning periods preceding and succeeding is changed is detected for each signal electrode, and if there is no change, the voltage of the voltage generating means is detected. For a certain period within the scanning period corresponding to the switching period, the output is high impedance,
When there is a change, it is characterized in that the voltage switching means selects a signal voltage that is switched to the correction voltage level for a certain period within the scanning period.

[0021]

According to the structure of claim 1, the intersection of the signal electrode and the scanning electrode corresponds to each pixel of the liquid crystal panel, and the signal electrode to which the signal voltage is applied and the scanning electrode to which the scanning voltage is applied. The desired data is displayed on the liquid crystal panel by turning on the pixel corresponding to the intersection point of.

Here, in the signal side driving means, the display data of a certain scanning electrode (scanning line) is 1 for each signal electrode.
It detects if there is a change with respect to the data of the previous scanning line, outputs a normal signal voltage level when there is no change, and when there is a change, reduces the effective voltage due to waveform blunting due to the change. Since the correction voltage to be corrected is output for a certain period within the scanning period, it is possible to correct the decrease in the effective value due to the waveform blunting that occurs in the signal electrode. As a result, the effective values of all the signal electrodes can be made substantially constant, and crosstalk can be significantly reduced.

According to the second aspect of the invention, at least one level of the correction voltage is supplied from the voltage generating means to the signal side driving circuit, and the signal side driving means outputs the display data of a certain scanning line for each signal electrode. Whether or not there is a change with respect to the display data of the immediately preceding scan line is detected, and if there is no change, a normal signal voltage level is output. If there is a change, a fixed period within the scan period, Since the means for outputting the correction voltage is provided, it is possible to correct the decrease in the effective value due to the waveform blunting that occurs in the signal electrode. This makes it possible to make the effective values of all signal electrodes approximately constant,
Crosstalk can be significantly reduced.

According to the third aspect of the invention, the voltage generating means including the voltage switching means supplies the correction voltage to the signal side driving means instead of the normal signal voltage level for a certain period during the scanning period, while The output stage of the side driving means has a configuration in which a normal signal voltage level can be selected or the output can be set to a high impedance, and the display data of a certain scan line for each signal electrode is the scan line immediately before that. If there is no change, the output is set to high impedance for a certain period within the scanning period corresponding to the voltage switching period of the voltage generating means, and if there is a change, Is supplied from the voltage generating means,
Since the means for selecting the voltage level is provided, it is possible to correct the decrease in the effective value due to the waveform blunting that occurs in the signal electrode. As a result, the effective values of all the signal electrodes can be made substantially constant, and crosstalk can be significantly reduced.

[0025]

EXAMPLES Examples of the present invention will be specifically described below.

(First Embodiment) A first embodiment of the present invention will be described below.

FIG. 1 is a block diagram schematically showing the structure of a liquid crystal display device according to the present invention. This liquid crystal display device includes a plurality of scanning electrodes Y1 to Y8 and a plurality of signal electrodes X1 to X8.
Liquid crystal panel 1 in which X8 and X8 are arranged to intersect with each other
A scan side drive circuit 3 for applying a voltage to the scan electrodes Y1 to Y8 line-sequentially, and a signal side drive circuit 2 for applying a signal voltage based on display data to the signal electrodes X1 to X8.
A power supply circuit 4 for generating a voltage necessary for driving the scanning side driving circuit 3 and the signal side driving circuit 2, and a control circuit 5 for controlling the scanning side driving circuit 3 and the signal side driving circuit 2.
It has and. For simplification of description, the number of each of the above-mentioned electrodes is set to eight, and in the following description, these electrodes are driven at 1/8 duty, and the inversion signal cycle for AC drive is 3 scanning lines. The case is given as an example.

In the basic driving method of this embodiment, the scan electrodes Y1 to Y8 are sequentially scanned according to the input scan clock LP and scan start signal FLM, and the scan side drive circuit 3
Via the power supply circuit 4 at the time of selection via the selection voltage V1, V
5 and the non-selection voltage V3 is applied at the time of non-selection. On the other hand, in this method, an ON voltage or an OFF voltage supplied from the power supply circuit 4 is applied to the signal electrodes X1 to X8 in accordance with display data, thereby driving the liquid crystal display device. This basic driving method is the same as the conventional one. Next, the part of this embodiment different from the conventional one will be described.

As shown in FIG. 2, for example, the signal side drive circuit 2 includes a shift register 11 for transferring the display data D by a data shift clock CK and a LP when the display data D for one scanning line is completely transferred. Based on the A latch 12 that holds the data of the scan line by a signal, the B latch 13 that also holds the display data of the previous scan line by the LP signal, and the alternating signal FR and the correction period control signal T1 An output control circuit 14 that detects continuity or discontinuity of display data from the output of the A latch 12 and the output of the B latch 13 and outputs a 2-bit signal for selecting an output voltage, a level shifter 15, and an output control circuit 14 Outputs either the normal signal voltage V2, V4 or the correction voltage V2 ', V4' to the signal electrode based on the signal from It is composed mainly of an output driver 16. that. Note that the correction voltages V2 'and V4'
Is a voltage value having a relationship of V2 <V2 ′ and V4 ′ <V4, and both are supplied from the power supply circuit 4.

The output control circuit 14 can be easily constructed by a general-purpose logic circuit. That is, for example, as shown in FIG. 3, the output control circuit 14 receives EXOR (exclusively) to which the display data Dn of a certain scanning period and the display data Dn-1 of the scan electrode immediately before the display data Dn are input. OR gate 51 and display data D
EXOR gate 5 to which n and the AC signal FR are input
2 and an AND (logical product) gate 53 to which the correction period control signal T1 for setting the period for applying the correction voltage and the output of the EXOR gate 51 are input. The EXOR gate 51 detects whether the display data is continuous or discontinuous. That is,
The EXOR gate 51 has display data Dn and display data D.
Only if n-1 and are entered and they are different,
This is because the H level is output to the output and it is detected that the data has changed.

The output control circuit 14 having the configuration shown in FIG. 3 operates based on the truth table of Table 1, and AN
Output OUT1 of D gate 53 and EXOR gate 52
The 2-bit signal of the output OUT2 of the above is supplied to the output driver 16. Based on this, the output driver 16 outputs V2, V
One of four voltage values of 4, V2 'and V4' is selectively output to the signal electrode.

[0032]

[Table 1]

Next, the operation of the signal side drive circuit 2 of FIG. 2 will be described below with reference to the time chart of FIG. FIG.
4A shows the waveform of the scanning clock LP, FIG. 4B shows the correction period control signal T1, and FIG. 4C shows the output of the signal side drive circuit in the conventional drive without using the correction voltage.

A correction period control signal T1 indicating a correction period is input to the output control circuit 14 in the signal side drive circuit 2, and the output driver 16 follows the truth table of Table 1 and the previous scanning line. When the display data Dn of the scanning line is different from the display data Dn-11 of the above, the correction voltage (V2 ′ or V2
4 ') is output. On the other hand, in a portion where the same display data continues over two scan electrodes, a normal signal voltage (V2 or V4) is output even when T1 is H.

Therefore, the signal side drive circuit 2 is configured to apply a correction voltage for correcting the blunt waveform of the signal side electrode voltage during the drive period of one scanning line. With such a configuration, as shown in FIG. 4D, it is possible to apply the signal voltage on which the correction voltage is superimposed in the scanning period immediately after the voltage of the signal side electrode is changed by the display data. Become. Therefore, by adjusting the application period and the voltage value of the correction voltage to the optimum values according to the size of the liquid crystal panel or the characteristics of the liquid crystal material, the effective value can be obtained for all the signal electrodes regardless of the display data. They can be the same, and as a result, crosstalk can be greatly reduced. It should be noted that FIG. 4E shows an output voltage waveform of the signal side drive circuit in consideration of the waveform dullness.
As shown in this figure, the application period and voltage value of the correction voltage are set so as to compensate for this dullness. The application period is not limited to a fixed period within the scanning period, and may be set to the entire period at a level where the correction voltage is lowered. This also applies to the following.

In this embodiment, two correction voltages V2 'and V4' are used as the correction voltages on the signal side, but only one of them is used for the simplification of the circuit and the like. The same effect can be obtained by increasing the correction amount per time accordingly.

Usually, a plurality of signal side drive circuits are formed as an IC and used in many cases. At this time, for example, the correction period is slightly changed for each IC arranged in the lateral direction of the liquid crystal panel, It is also possible to correct the difference in the degree of crosstalk depending on the location in the liquid crystal panel.

(Second Embodiment) A second embodiment of the present invention will be described below.

FIG. 5 is a block diagram schematically showing the structure of the liquid crystal display device according to the present invention. This liquid crystal display device includes a plurality of scanning electrodes Y1 to Y8 and a plurality of signal electrodes X1 to X8.
Liquid crystal panel 1 in which X8 and X8 are arranged to intersect with each other
A scanning side driving circuit 3 for applying a voltage to the scanning electrodes Y1 to Y8 line-sequentially, and a signal side driving circuit 22 for applying a signal voltage based on display data to the signal electrodes X1 to X8.
A power supply circuit 24 for generating a voltage necessary for driving the scanning side driving circuit 3 and the signal side driving circuit 22; and a control circuit 25 for controlling the scanning side driving circuit 3 and the signal side driving circuit 22. . In addition, for simplification of description,
The above-mentioned number of each electrode is eight, and in the following description, the case where these electrodes are driven at 1/8 duty and the inversion signal period for AC drive is three scanning lines is taken as an example. .

In the basic driving method of this embodiment, the scan electrodes Y1 to Y8 are sequentially scanned according to the input scan clock LP and scan start signal FLM, and the power supply circuit is selected at the time of selection via the scan side drive circuit 23. Select voltage V1, V from 24
5 and the non-selection voltage V3 is applied at the time of non-selection. On the other hand, in this method, an ON voltage or an OFF voltage supplied from the power supply circuit 24 is applied to the signal electrodes X1 to X8 in accordance with display data, thereby driving the liquid crystal display device. This basic driving method is the same as the conventional one.
Next, the part of this embodiment different from the conventional one will be described.

As shown in FIG. 6, for example, the signal side drive circuit 22 has a shift register 31 for transferring the display data D by a data shift clock CK and an LP signal at the time when the display data for one scanning line has been transferred. Based on the A latch 32 that holds the display data of the scan line, the B latch 33 that also holds the display data of the previous scan line by the LP signal, and the alternating signal FR and the correction period control signal T2, From the output of the A-latch 32 and the output of the B-latch 33, a control circuit 34 that detects continuity or discontinuity of display data and outputs a 2-bit signal for selecting an output voltage, a level shifter 35, and an output control circuit 34 An output that selects one of the normal signal voltages V2, V4 or a high impedance output based on the signal of It is composed mainly from the driver 36..

The output control circuit 34 can be easily constructed by a logic circuit. For example, it can be realized with the completely same configuration as the circuit shown in FIG. 3 shown in the first embodiment. The output control circuit 34 configured by the logic circuit of FIG. 3 performs the operation based on the truth table of Table 2, and outputs the 2-bit signal of the output 0UT1 of the AND gate 53 and the output OUT2 of the EX0R gate 52 to the output driver 36. input. Based on this, the output connected to the signal electrode is V
2 "power line voltage value, V4" power line voltage value,
Alternatively, one of the three states of high impedance (HZ) is selected.

[0043]

[Table 2]

However, the voltage is set to the signal voltage V by the voltage switching circuit 40 included in the power supply circuit 24 illustrated in FIG.
The correction voltages V2 'and V4' are superposed on 2 and V4 at the same timing as the correction period control signal T2, and this state is shown in FIG.

Therefore, except for the period when the correction period control signal T2 is H and the output having the high impedance (that is, the output which has changed as compared with the display data of the previous scanning line).
Is applied with the correction voltage V2 'or V4' via the V2 "power supply line and the V4" power supply line. In Table 2, the portions indicated by (V2 ′) and (V4 ′) correspond to them.

Therefore, the signal side drive circuit 22 is
When the signal-side electrode waveform becomes dull during the driving period of one scanning line, a correction voltage for correcting it is applied. With this configuration, also in the second embodiment, the signal side output finally obtained is the same as that in FIG. 4 shown in the first embodiment, and as a result, the voltage of the signal side electrode is changed by the display data. It is possible to apply the signal voltage on which the correction voltage is superimposed in the scanning period immediately after the change. Therefore, by appropriately adjusting the application period and voltage value of this correction voltage, the effective value of the applied waveform can be made the same for all the signal electrodes regardless of the display data, resulting in crosstalk. It is possible to significantly reduce it.

Further, according to the configuration of the second embodiment, as is apparent from FIG. 6, the drive voltage line supplied to the signal side drive circuit and the switching element of the output section are different from those of the first embodiment. The number may be half, and the chip area of the signal side drive circuit, which is usually integrated into an IC, is significantly reduced, which is a great advantage in terms of cost reduction and miniaturization.

In the second embodiment, an example in which two correction voltages V2 "and V4" are used is shown. However, in the second embodiment as well, as in the first embodiment, circuits such as circuits are used. For simplification, the same effect can be obtained even if only one of them is used and the correction amount per time is increased accordingly.

Although the first and second embodiments have been described above, the configuration of the present invention is not limited to these embodiments, and is input from the outside as a correction period control signal, for example. Although a signal is used, the signal may be generated inside, for example, the signal side drive circuit.

Further, in each of the above-described embodiments, the non-selection potential (V3) on the scanning side is set to GND based on the voltage averaging method as the driving method of the liquid crystal panel, and the bias ratio is set to 1 / a. ± Vop (1/11 / a) is applied as the scanning side selection potential (V1, V5) of the above, and ± (Vop / a) is applied as the voltage (V2, V4) according to the display data applied to the signal side. However, the present invention is not limited to this. For example, it is possible to adopt a driving method in which the applied potential is different from the above. That is, as the driving method, two types of Vop (1-1 / a) and Vop / a are used as the non-selection potential on the scanning side, and the corresponding selection potential is Vop or GN.
D, and Vop, Vo according to the display data on the signal side.
A method of applying a potential of p (1-2 / a) or 2Vop / a, GND is applicable. However, at this time, since there are four signal potentials necessary for the signal side driving circuit, it is necessary to appropriately increase the necessary correction voltage and the like accordingly.

Further, the present invention is caused not only by the liquid crystal display device capable of only binary display (including gradation display by frame thinning) but also by waveform blunting even in the case of pulse width modulation or amplitude modulation. It can be effectively applied to crosstalk.

FIG. 12 shows a simulated waveform of an applied waveform to the liquid crystal panel realized by the present invention, 320 dots wide ×
FIG. 6 is a diagram showing measurement points A and B when the crosstalk rate is measured by applying the invention to a color display STN liquid crystal panel driven at 240 dots in the vertical direction and a frame frequency of 120 Hz. Here, the crosstalk rate is expressed as {(Lx, where L is the brightness of the white display on the whole surface at the measurement points A and B shown in FIG. 12 and Lx is the display as shown in the figure.
/ L) -1} × 100 (%).

As a result, the shadowing rate at measurement point A was -17.6% at 0% and at the measurement point B at -12.
3% was significantly improved to -2.1%.

[0054]

As described in detail above, according to the present invention, when the signal side voltage applied to the signal electrode of the liquid crystal panel changes depending on the display data, the effective value due to the waveform bluntness. Since the liquid crystal display device is provided with a means for correcting the deterioration of the liquid crystal display device, it is possible to realize a liquid crystal display device capable of significantly reducing crosstalk that significantly impairs display quality. Further, in the present invention, compared with the conventional crosstalk reduction method,
Both reduction of power consumption and increase of contrast can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is an internal block diagram of a signal side drive circuit in the first embodiment of the present invention.

FIG. 3 is a logic circuit diagram showing a part of a signal side drive circuit in the first embodiment.

FIG. 4 is a timing chart showing the operation of the first embodiment.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is an internal block diagram of a signal side drive circuit according to a second embodiment of the present invention.

FIG. 7 is an internal block diagram of a voltage generating circuit according to a second embodiment of the present invention.

FIG. 8 is a timing chart showing an operation of the voltage generating circuit according to the second embodiment of the present invention.

FIG. 9 is a block diagram showing a conventional technique.

FIG. 10 is a timing chart showing an operation in an ideal state of the conventional technique.

FIG. 11 is a timing chart showing the cause of crosstalk in the prior art.

FIG. 12 is a diagram showing measurement points A and B when the present invention is applied to a STN liquid crystal panel for color display and the crosstalk rate is measured.

[Explanation of symbols]

 1 liquid crystal panel 2 signal side drive circuit 3 scanning side drive circuit 4 power supply circuit 5 control circuit 11 shift register 12 A latch 13 B latch 14 output control circuit 15 level shifter 16 output driver 31 shift register 32 A latch 33 B latch 34 output control circuit 35 level shifter 36 output driver 101 liquid crystal panel 102 signal side drive circuit 103 scanning side drive circuit 104 power supply circuit 105 control circuit

Claims (3)

[Claims] 1. A liquid crystal display device comprising a liquid crystal panel in which a liquid crystal layer is provided between a plurality of signal electrodes and a plurality of scanning electrodes which are arranged so as to intersect with each other, for displaying the liquid crystal panel. Signal side driving means for applying a voltage corresponding to the display data to the signal electrode, scanning side driving means for sequentially applying a scanning voltage to the scanning electrode, the signal side driving means and the scanning side driving means, respectively. And a voltage generating means for supplying a voltage required for driving the signal side, the signal side driving means detects, for each signal electrode, whether or not the display data in successive scanning periods changes, and there is no change. In this case, the normal signal voltage level is output, and when there is a change, a correction voltage for correcting the effective voltage drop due to the waveform blunting due to the change is output for a certain period within the corresponding scanning period. Liquid crystal display device. 2. The voltage generating means is configured to generate the correction voltage of at least one level in addition to a normal signal voltage level as a voltage level to be supplied to the signal side driving means, and the signal side The driving means is configured such that the output stage thereof can selectively output the correction voltage of at least one level supplied from the voltage generating means in addition to the normal signal voltage level, and the phase of each of the signal electrodes is changed. It is detected whether or not the display data in the preceding and following scanning periods change, and if there is no change, a normal signal voltage level is output. If there is a change, the correction is performed for a certain period within the corresponding scanning period. The liquid crystal display device according to claim 1, which outputs a voltage. 3. The voltage generating means has a function of generating at least one level of the correction voltage in addition to a normal signal voltage level as a voltage level to be supplied to the signal side driving means, and a corresponding scanning period. A voltage switching means for outputting the correction voltage in place of the normal signal voltage level for a certain period of time in the above and supplying it to the signal side driving means, and the signal side driving means has an output stage The signal voltage level is selected or the output is made to have a high impedance, and it is detected for each signal electrode whether or not the display data in successive scanning periods change, and if there is no change, it is detected. The output is set to high impedance for a certain period within the scanning period corresponding to the voltage switching period of the voltage generating unit, and when there is a change, the voltage switching unit causes the output to fall within the scanning period. Kicking a period of time, the liquid crystal display device according to claim 1 for selecting the signal voltage is switched to the correct voltage level.